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Transverse momentum dependence of J/psi polarization at midrapidity in p+p collisions at sqrt(s)=200 GeV

The PHENIX collaboration Adare, A. ; Afanasiev, S. ; Aidala, C. ; et al.
Phys.Rev.D 82 (2010) 012001, 2010.
Inspire Record 839540 DOI 10.17182/hepdata.141077

We report the measurement of the transverse momentum dependence of inclusive J/psi polarization in p+p collisions at sqrt(s)=200 GeV performed by the PHENIX Experiment at RHIC. The polarization is studied in the helicity, Gottfried-Jackson, and Collins-Soper frames for p_T < 5 GeV/c and |y| < 0.35. The J/psi polarization in the helicity and Gottfried-Jackson frames is consistent with zero for all transverse momenta, with a slight (1.8 sigma) trend towards longitudinal polarization for transverse momenta above 2 GeV/c. No conclusion is allowed due to the limited acceptance in the Collins-Soper frame and the uncertainties of the current data. The results are compared to observations for other collision systems and center of mass energies and to different quarkonia production models.

3 data tables

$J/\psi$ yield times dielectron branching ratio ($B$) after detector acceptance and efficiency corrections for the real data with $A$ = 28.7 $\pm$ 1.0 nb/GeV/$c$, $b$ = 3.41 $\pm$ 0.21 GeV/$c$, and $n$ = 4.6 $\pm$ 0.4.

$J/\psi$ polarization parameter ($\lambda_{J/\psi}$) versus transverse momentum ($p_T$).

$J/\psi$ polarization parameter ($\lambda_{J/\psi}$) versus transverse momentum ($p_T$).


Detailed measurement of the $e^+ e^-$ pair continuum in $p+p$ and Au+Au collisions at $\sqrt{s_{NN}} = 200$ GeV and implications for direct photon production

The PHENIX collaboration Adare, A. ; Afanasiev, S. ; Aidala, C. ; et al.
Phys.Rev.C 81 (2010) 034911, 2010.
Inspire Record 838580 DOI 10.17182/hepdata.145190

PHENIX has measured the e^+e^- pair continuum in sqrt(s_NN)=200 GeV Au+Au and p+p collisions over a wide range of mass and transverse momenta. The e^+e^- yield is compared to the expectations from hadronic sources, based on PHENIX measurements. In the intermediate mass region, between the masses of the phi and the J/psi meson, the yield is consistent with expectations from correlated c^bar-c production, though other mechanisms are not ruled out. In the low mass region (below the phi) the p+p inclusive mass spectrum is well described by known contributions from light meson decays. In contrast, the Au+Au minimum bias inclusive mass spectrum in this region shows an enhancement by a factor of 4.7+/-0.4(stat)+/-1.5(syst)+/-0.9(model) At low mass (m_ee<0.3 GeV/c^2) and high p_T (1<p_T<5 GeV/c) an enhanced e^+e^- pair yield is observed that is consistent with production of virtual direct photons. This excess is used to infer the yield of real direct photons. In central Au+Au collisions, the excess of the direct photon yield over the p+p is exponential in p_T, with inverse slope T=221+/-19(stat)+/-19(syst) MeV. Hydrodynamical models with initial temperatures ranging from T_init ~=300--600 MeV at times of 0.6--0.15 fm/c after the collision are in qualitative agreement with the direct photon data in Au+Au. For low p_T<1 GeV/c the low mass region shows a further significant enhancement that increases with centrality and has an inverse slope of T ~=100 MeV. Theoretical models under predict the low mass, low p_T enhancement.

113 data tables

(Color online) Inclusive mass spectrum of $e^+e^-$ pairs in the PHENIX acceptance in $p$+$p$ collisions compared to the expectations from the decays of light hadrons and correlated decays of charm, bottom, and Drell-Yan. The contribution from hadron decays is independently normalized based on meson measurements in PHENIX. The bottom panel shows the ratio of data to the cocktail of known sources. The systematic uncertainties of the data are shown as boxes, while the uncertainty on the cocktail is shown as band around 1.

(Color online) Inclusive mass spectrum of $e^+e^-$ pairs in the PHENIX acceptance in minimum-bias Au+Au compared to expectations from the decays of light hadrons and correlated decays of charm, bottom, and Drell-Yan. The charm contribution expected if the dynamic correlation of $c$ and $\bar{c}$ is removed is shown separately. Statistical (bars) and systematic (boxes) uncertainties are shown separately. The contribution from hadron decays is independently normalized based on meson measurements in PHENIX. The bottom panel shows the ratio of data to the cocktail of known sources. The systematic uncertainties of the data are shown as boxes, while the uncertainty on the cocktail is shown as band around 1.

(Color online) Inclusive mass spectrum of $e^+e^-$ pairs in the PHENIX acceptance in minimum-bias Au+Au compared to expectations from the decays of light hadrons and correlated decays of charm, bottom, and Drell-Yan. The charm contribution expected if the dynamic correlation of $c$ and $\bar{c}$ is removed is shown separately. Statistical (bars) and systematic (boxes) uncertainties are shown separately. The contribution from hadron decays is independently normalized based on meson measurements in PHENIX. The bottom panel shows the ratio of data to the cocktail of known sources. The systematic uncertainties of the data are shown as boxes, while the uncertainty on the cocktail is shown as band around 1.

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First proton--proton collisions at the LHC as observed with the ALICE detector: measurement of the charged particle pseudorapidity density at sqrt(s) = 900 GeV

The ALICE collaboration Aamodt, K ; Abel, N ; Abeysekara, U ; et al.
Eur.Phys.J.C 65 (2010) 111-125, 2010.
Inspire Record 838352 DOI 10.17182/hepdata.53751

On 23rd November 2009, during the early commissioning of the CERN Large Hadron Collider (LHC), two counter-rotating proton bunches were circulated for the first time concurrently in the machine, at the LHC injection energy of 450 GeV per beam. Although the proton intensity was very low, with only one pilot bunch per beam, and no systematic attempt was made to optimize the collision optics, all LHC experiments reported a number of collision candidates. In the ALICE experiment, the collision region was centred very well in both the longitudinal and transverse directions and 284 events were recorded in coincidence with the two passing proton bunches. The events were immediately reconstructed and analyzed both online and offline. We have used these events to measure the pseudorapidity density of charged primary particles in the central region. In the range |$\eta$| < 0.5, we obtain dNch/deta = 3.10 $\pm$ 0.13 (stat.) $\pm$ 0.22 (syst.) for all inelastic interactions, and dNch/deta = 3.51 $\pm$ 0.15 (stat.) $\pm$ 0.25 (syst.) for non-single diffractive interactions. These results are consistent with previous measurements in proton-antiproton interactions at the same centre-of-mass energy at the CERN SppS collider. They also illustrate the excellent functioning and rapid progress of the LHC accelerator, and of both the hardware and software of the ALICE experiment, in this early start-up phase.

2 data tables

Pseudorapidity dependence of DN/DETARAP in Inelastic (INEL) and Non-Single-Diffractive (NSD) collisions. Note that the plot in the paper shows only statistical errors.

Pseudorapidity density for |ETARAP|<0.5 for Inelastic (INEL) and Non-Single-Diffractive (NSD) collisions.


Cross sections and Rosenbluth separations in 1H(e, e'K+)Lambda up to Q2=2.35 GeV2

The Jefferson Lab Hall A collaboration Coman, M. ; Markowitz, P. ; Aniol, K.A. ; et al.
Phys.Rev.C 81 (2010) 052201, 2010.
Inspire Record 837422 DOI 10.17182/hepdata.54197

The kaon electroproduction reaction 1H(e,e'K+)Lambda was studied as a function of the virtual-photon four-momentum, Q2, total energy, W, and momentum transfer, t, for different values of the virtual- photon polarization parameter. Data were taken at electron beam energies ranging from 3.40 to 5.75 GeV. The center of mass cross section was determined for 21 kinematics corresponding to Q2 of 1.90 and 2.35 GeV2 and the longitudinal, sigmaL, and transverse, sigmaT, cross sections were separated using the Rosenbluth technique at fixed W and t. The separated cross sections reveal a flat energy dependence at forward kaon angles not satisfactorily described by existing electroproduction models. Influence of the kaon pole on the cross sections was investigated by adopting an off-shell form factor in the Regge model which better describes the observed energy dependence of sigmaT and sigmaL.

11 data tables

Measured values of the separated cross section at Q**2 = 2.35 GeV**2 and W = 1.85 GeV.. Errors contain both statistics and systematics.

Measured values of the separated cross section at Q**2 = 1.90 GeV**2.. Errors contain both statistics and systematics.

Measured values of the separated cross section at Q**2 = 2.35 GeV**2.. Errors contain both statistics and systematics.

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Measurement of the ttbar cross section using high-multiplicity jet events

The D0 collaboration Abazov, V.M. ; Abbott, B. ; Abolins, M. ; et al.
Phys.Rev.D 82 (2010) 032002, 2010.
Inspire Record 837547 DOI 10.17182/hepdata.52975

We present a measurement of the ttbar cross section using high-multiplicity jet events produced in ppbar collisions at sqrt{s}=1.96 TeV. These data were recorded at the Fermilab Tevatron collider with the D0 detector. Events with at least six jets, two of them identified as b jets, were selected from a 1 fb-1 data set. The measured cross section, assuming a top quark mass of 175 GeV/c^2, is 6.9 \pm 2.0 pb, in agreement with theoretical expectations.

1 data table

Measured top topbar cross section at two values of the top mass.


Measurement of the WW+WZ Production Cross Section Using the Lepton+Jets Final State at CDF II

The CDF collaboration Aaltonen, T. ; Adelman, J. ; Alvarez Gonzalez, B. ; et al.
Phys.Rev.Lett. 104 (2010) 101801, 2010.
Inspire Record 837610 DOI 10.17182/hepdata.54292

We report two complementary measurements of the WW+WZ cross section in the final state consisting of an electron or muon, missing transverse energy, and jets, performed using p\bar{p} collision data at sqrt{s} = 1.96 TeV collected by the CDF II detector. The first method uses the dijet invariant mass distribution while the second more sensitive method uses matrix-element calculations. The result from the second method has a signal significance of 5.4 sigma and is the first observation of WW+WZ production using this signature. Combining the results gives sigma_{WW+WZ} = 16.0 +/- 3.3 pb, in agreement with the standard model prediction.

3 data tables

Cross section from the combined analysis.. Error is combined statistics and systematics.

Cross section from method one.

Cross section from method two.


Measurement of the Inclusive Isolated Prompt Photon Cross Section in ppbar Collisions at sqrt{s} = 1.96 TeV using the CDF Detector

The CDF collaboration Aaltonen, T. ; Adelman, J. ; Alvarez Gonzalez, B. ; et al.
Phys.Rev.D 80 (2009) 111106, 2009.
Inspire Record 834437 DOI 10.17182/hepdata.53755

A measurement of the cross section for the inclusive production of isolated photons by the CDF experiment at the Fermilab Tevatron collider is presented. The measurement covers the pseudorapidity region |eta^gamma|<1.0 and the transverse energy range E_T^gamma>30 GeV and is based on 2.5/fb of integrated luminosity. The sample is almost a factor of seven larger than those used for recent published results and extends the E_T^gamma coverage by 100 GeV. The result agrees with next-to-leading order perturbative QCD calculations within uncertainties over the range 50<E_Tgamma<400 GeV, though the energy spectrum in the data shows a steeper slope at lower E_T^gamma.

1 data table

Measured inclusive isolated photon cross section.


Measurement of Inclusive Neutral Current Neutral Pion Production on Carbon in a Few-GeV Neutrino Beam

The SciBooNE collaboration Kurimoto, Y. ; Alcaraz-Aunion, J.L. ; Brice, S.J. ; et al.
Phys.Rev.D 81 (2010) 033004, 2010.
Inspire Record 835586 DOI 10.17182/hepdata.53757

The SciBooNE Collaboration reports inclusive neutral current neutral pion production by a muon neutrino beam on a polystyrene target (C8H8). We obtain (7.7 \pm 0.5(stat.) \pm 0.5 (sys.)) x 10^(-2) as the ratio of the neutral current neutral pion production to total charged current cross section; the mean energy of neutrinos producing detected neutral pions is 1.1 GeV. The result agrees with the Rein-Sehgal model implemented in our neutrino interaction simulation program with nuclear effects. The spectrum shape of the neutral pion momentum and angle agree with the model. We also measure the ratio of the neutral current coherent pion production to total charged current cross section to be (0.7 \pm 0.4) x 10^(-2).

2 data tables

Ratio of inclusive NC PI0 production to the total CC cross section.

Ratio of NC coherent PI0 production to the total CC cross section.


Double Helicity Dependence of Jet Properties from Dihadrons in Longitudinally Polarized p+p Collisions at sqrt(s) = 200 GeV

The PHENIX collaboration Adare, A. ; Afanasiev, S. ; Aidala, C. ; et al.
Phys.Rev.D 81 (2010) 012002, 2010.
Inspire Record 833129 DOI 10.17182/hepdata.141612

It has been postulated that partonic orbital angular momentum can lead to a significant double-helicity dependence in the net transverse momentum of Drell-Yan dileptons produced in longitudinally polarized p+p collisions. Analogous effects are also expected for dijet production. If confirmed by experiment, this hypothesis, which is based on semi-classical arguments, could lead to a new approach for studying the contributions of orbital angular momentum to the proton spin. We report the first measurement of the double-helicity dependence of the dijet transverse momentum in longitudinally polarized p+p collisions at sqrt(s) = 200 GeV from data taken by the PHENIX experiment in 2005 and 2006. The analysis deduces the transverse momentum of the dijet from the widths of the near- and far-side peaks in the azimuthal correlation of the dihadrons. When averaged over the transverse momentum of the triggered particle, the difference of the root-mean-square of the dijet transverse momentum between like- and unlike-helicity collisions is found to be -37 +/- 88(stat) +/- 14(syst) MeV/c.

3 data tables

Values of derived $<z_T>$ and $\hat{x_h}$.

Helicity-averaged $\sqrt{<j^2_T>}$ and $\sqrt{<k^2_T>}$ for combined 2005 and 2006 data.

Difference in $\sqrt{<j^2_T>}$ and $\sqrt{<k^2_T>}$ for like- minus unlike-helicity combinations.


Measurement of the incoherent $\gamma d \to \phi p n$ photoproduction near threshold

The LEPS collaboration Chang, W.C. ; Miyabe, M. ; Nakano, T. ; et al.
Phys.Lett.B 684 (2010) 6-10, 2010.
Inspire Record 825381 DOI 10.17182/hepdata.54640

We report measurements of differential cross sections and decay asymmetries of incoherent $\phi$-meson photoproduction from the deuteron at forward angles using linearly polarized photons at \Eg=1.5-2.4 GeV. The nuclear transparency ratio for the deuteron shows a large suppression, and is consistent with the A-dependence of the ratio observed in a previous measurement with nuclear targets. The reduction for the deuteron cannot be adequately explained in term of isospin asymmetry. The present results suggest the need of refining our understanding of the $\phi$-N interaction within a nucleus.

7 data tables

Distribution of DSIG/DT from incoherent reaction GAMMA DEUT --> PHI P N for the incident photon energy ranges 1.57 to 1.67 and 1.67 to 1.77 GeV.

Distribution of DSIG/DT from incoherent reaction GAMMA DEUT --> PHI P N for the incident photon energy ranges 1.77 to 1.87 and 1.87 to 1.97 GeV.

Distribution of DSIG/DT from incoherent reaction GAMMA DEUT --> PHI P N for the incident photon energy ranges 1.97 to 2.07 and 2.07 to 2.17 GeV.

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